Climate Change 3

Kinkajou:. Let’s consider the variables that underwrite climate change/global warming.

Erasmus: .

Short-wavelength radiation
Even though it only accounts for a minuscule fraction of total solar radiation, the impact of solar UV, EUV and X-ray radiation on the Earth's upper atmosphere is profound. Solar UV flux is a major driver of stratospheric chemistry namely ozone formation, and increases in ionizing radiation significantly affect ionosphere-influenced temperature and electrical conductivity.

Clouds
Speculations about the effects of cosmic-ray changes over the cycle potentially include:
*  During solar minima more cosmic rays reach Earth, potentially creating ultra-small aerosol particles as precursors to Cloud condensation nuclei. Clouds formed from greater amounts of condensation nuclei are brighter, longer lived and likely to produce less precipitation.
* A change in cosmic rays could cause an increase in certain types of clouds, affecting Earth's albedo.

The amount of ultraviolet UVB light at 300 nm reaching the Earth's surface varies by a few percent over the solar cycle due to variations in the protective ozone layer. In the stratosphere, ozone is continuously regenerated by the splitting of O2 molecules by ultraviolet light.

Erasmus: . On Climate
Three proposed mechanisms mediate solar variations' climate impacts:
* Total solar irradiance ("Radiative forcing").
* Ultraviolet irradiance. The UV component varies by more than the total, so if UV were for some (as yet unknown) reason having a disproportionate presence, this might affect climate.
* Solar wind-mediated galactic cosmic ray changes, which may affect cloud cover.

It has been suggested that the solar cycle variation of 0.1% correlates with a variation of 0.18 K ±0.08 K (0.32 °F ±0.14 °F) in measured average global temperature between solar maximum and minimum.

Alternately, other scientists have proposed that these Recent findings indicate that intrinsic TSI variation has had a much larger role (up to 50%) in global warming during the industrial era than previously predicted by global circulation models (GCM’s).

The current scientific consensus, most specifically that of the IPCC, is that solar variations only play a marginal role in driving global climate change, since the measured magnitude of recent solar variation is much smaller than the forcing due to greenhouse gases. 

Goo: . But these conclusions are based on assumptions and inferences not experimentation. We live with and go along with the solar cycle. We have absolutely no capacity to make changes and to assess the effects of our changes.
Dr Axxxx: .  Best guesses by apelike mammals, are just guesses. Humanity does not have the experience yet to really model climate terribly well.

Also, average solar activity in the 2010s was no higher than in the 1950s (see above), whereas average global temperatures had risen markedly over that period. Seasonal variation Occurs. Solar maxima occurred in 1989, 2000 and 2014 while solar minima occurred in 1996 and 2008.

Goo: . Confusing unfortunately. Real World- Climate modelling is complex.

Solar Maximum

Kinkajou:. Let’s talk about what the historical record of isotopes tells us about solar activity.

Major events and approximate dates
Homeric minimum-this [15]
Start: 750 BCE
End: 550 BCE

Oort minimum
Start: 1040 CE
End: 1080 CE

Medieval maximum
Start: 1100
End: 1250

Wolf minimum
Start: 1280
End: 1350

Spörer Minimum
1450
1550

Maunder Minimum
Start: 1645
End: 1715

Dalton Minimum
Start: 1790
End: 1820

Modern Maximum
Start: 1933
End: 2008

Since observations began, solar cycles as short as 9 years and as long as 14 years have been observed, Significant amplitude variations also occur.

Kinkajou:. Let’s move on and talk about the other variables that affect climate change. Dust production by human beings must certainly be a major factor – impacting on the albedo and radiation absorption depending on the type of dust.

Erasmus: . Anthropogenic Dust Emissions are defined as of two types: (1) arising from human land uses that directly emit dust to the atmosphere (e.g., cultivation) or disturbed soils and/or vegetation, so that the land surface is more susceptible to erosive winds; and (2) arising from human modification of the climate, which in turn modifies wind erosivity, land erodibility, and the magnitude of dust emissions.

Implicit in studies framed by these definitions has been an assumption that dust emissions prior to the industrial era were natural, although land cover globally has been modified by human activities since the late Pleistocene. The Pleistocene (often referred to as the Ice Age) is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations.

While these definitions clearly state the potential different causes of anthropogenic dust, neither conveys the mechanisms, the complexity of the processes, or how this complexity can be resolved consistently to quantify dust emission.

Anthropogenic impacts on the wind erodibility and dust emission potential of landscapes may be extensive or intensive in terms of the area affected and the degree of land surface modification .

Livestock grazing and trampling of rangelands can modify the foliar cover and height of vegetation and break down protective soil crusts in the short term or act as a driver of long-term ecological (land cover) change . These impacts typically occur at the landscape scale (extensive), but can also be concentrated (intensive effects) —for example, around livestock watering points that may become locally degraded and susceptible to accelerated wind erosion (i.e., net soil loss) and dust emission).

Cropland management practices can create mosaic landscapes with dust emission hot spots arising in response to tillage practices and crop rotations within individual fields.
Similarly, intensive landscape disturbances resulting from altered hydrological regimes (e.g., river diversion), energy development, graded road networks, and off-road vehicle activity, modify land cover and potentially accelerate point-source dust emissions .

Global dust modeling suggests that the anthropogenic contribution to atmospheric dust loads today range between 10% and 60%, that is, between 90Mt and 2000Mt per year . Since the mid-Holocene, regional atmospheric dust loads have increased concurrently with the expansion of human land-use activities; for example, by up to 500% in North America. (The Holocene Epoch began 12,000 to 11,500 years ago at the close of the Paleolithic Ice Age and continues through today.)

Anthropogenic dust emissions resulting from direct human modification of landscapes have been estimated from deposition records, revealing order-of-magnitude changes in dust emissions that correlate with the timing of agropastoral development and drought .

Assessments of future anthropogenic dust creation are uncertain with different methods rendering predictions of increased, stable or decreased levels of dust in the future.
Uncertainty in the magnitude of anthropogenic dust emissions remains large. WE need to understand dust generation to know how to combat land degradation and desertification, provide food security, and enable Sustainable Development Goals to be achieved .

Satellite remote sensing has enabled detection of dust source locations at higher spatial resolutions .

Wind effects on Climate
The potentially devastating impacts of LULCC (land use and land cover change ) and land management-induced wind erosion for agroecological systems and the societies that depend on them .

Wind erosion has been a key resource concern for land managers globally since the introduction of European farming practices and vast expansion of croplands. Regional studies have suggested that changes in surface wind speeds are responsible rather than land cover change, as the main mechanism for dust creation / generation. Extensive field and wind tunnel experimentation have provided a basis for understanding the causal mechanisms of anthropogenic wind erosion and dust emission at small property scales .

Nevertheless, in many cases the mechanisms remain unclear as climate variability, changes in land surface roughness, and changes in erodible sediment supply may all be responsible for the observed changes in global dust emissions .

Goo: . I think the moral of the story is that it is very difficult to model dust production. One basic issue is whether human changes are extensive or intensive. And there can be multiple layers of these factors over a single region.

Kinkajou:. If you cannot model accurately, you cannot predict very accurately either.

Erasmus: . Wind erosion accelerated by LULCC (land use and land cover change ) influences soil nutrients and bio-geo-chemical cycles, the land surface energy budget, and climate, with feedbacks that can promote further land cover change, dryland expansion, and increased dust emissions. For example, wind erosion of Sahelian (sub-Saharan) croplands has been found to reduce soil nutrient levels by approximately the same order-of-magnitude as the uptake typically required by millet in 1 year - reducing the land potential for successful crop production.

Goo: . Again, you can see the complexity in modeling Degraded and Wind eroded soils - producing dust but also losing nutrients, and we have not even mentioned water effects as well.

Kinkajou:. Land cover change is often characterized by one or more changes to vegetation foliar cover, canopy height, and canopy spatial configuration, which influence dust emission.

Model insensitivity to vegetation spatial patterns limits the ability of assessments to detect the impacts of land cover change.

Biosphere Modelling

Illustration of interactions between anthropogenic land use and land cover change (LULCC) and the dust cycle.

Human land use activities, such as agriculture and livestock grazing, potentially cause soil surface disturbance and changes in vegetation species composition, structure and spatial patterns.

Goo: . Many opportunities remain to improve assessment methods and models and to explore the gaps in our understanding of human-dust cycle interactions.

Kinkajou:. This Defining what constitutes anthropogenic dust with the specificity to unpack the causal mechanisms is a requisite step toward developing an assessment framework. Even the definition of what is anthropogenic dust needs consideration.

Erasmus: . Anthropogenic dust emissions may be considered:
(1) a departure of the magnitude of dust emissions from the established “normal” range for a land cover type associated with a gradual or abrupt transition (regime shift) from one ecological state and land use to another (e.g., grassland to shrubland, or grassland to cropland), where the transition can be attributed to human activities, and
(2) a departure of the magnitude of dust emissions within an ecological state and land use (e.g., grassland) that is outside the natural variability for that state and where the within-state ground cover change (e.g., reduction in foliar cover or protective soil crusts) can be attributed to human activities .

Erasmus: . Due to this complexity, in many cases quantifying the anthropogenic dust contribution may not be straightforward or even possible.

These approaches suggest that resolving anthropogenic impacts on wind erosion and dust emission may be most effective at the landscape scale, at which land management-land cover interactions take place.

Anthropogenic LULCC has potentially massive impacts on rates of wind-driven soil erosion and dust emission, but the magnitude of these impacts remains highly uncertain.

Kinkajou:. Let’s talk about albedo. Changes in albedo would have to be a major factor in causing climate change. The Earth's climate depends on a balance of incoming and outgoing energy from the sun, which is determined by albedo.

Erasmus: .
Albedo (from Latin albedo 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that reflects all incident radiation.

The lower the albedo, the more radiation from the Sun that gets absorbed by the planet, and temperatures will rise. If the albedo is higher, and the Earth is more reflective, more of the radiation is returned to space, and the planet cools.

Unless given for a specific wavelength (spectral albedo), albedo refers to the entire spectrum of solar radiation. Due to measurement constraints, it is often given for the spectrum in which most solar energy reaches the surface (between 0.3 and 3 microns). This spectrum includes visible light (0.4–0.7 microns), which explains why surfaces with a low albedo appear dark (e.g., trees absorb most radiation), whereas surfaces with a high albedo appear bright (e.g., snow reflects most radiation).

The average albedo of the Earth from the upper atmosphere, its planetary albedo, is 30–35% (0.3) because of cloud cover.

Kinkajou:. It has a significant effect on the equilibrium temperature of the Earth as it changes how much solar energy is reflected by the Earth as opposed to how much is absorbed. 

The Earth's surface doesn't have a single albedo, rather a number of different albedos that are combined into a single number to accurately describe how the Earth reflects and absorbs solar energy as a whole.

As the world warms the Earth's albedo shifts.

The amount of ice covering the planet is decreased due to the progressive melting of the ice caps, causes a decrease in the area of white surfaces, leading to less energy to be reflected and more to be absorbed. This process warms the Earth even more.
So, melting ice lowers albedo. If a marginally snow-covered area warms, snow tends to melt, lowering the albedo, and hence leading to more snowmelt because more radiation is being absorbed by the snowpack (the ice–albedo positive feedback).

Earth's Albedo

Erasmus: . The greenhouse effect can also change the albedo of the Earth. by trapping in more infrared radiation with the increased number of greenhouse gases ( most notably water vapour), in the atmosphere, This effect on global warming is complex.. If temperatures are higher, evaporation increases, increasing albedo (clouds) and reducing global warming effects . This effect buffers the effect of greenhouse gases on planetary temperature.

Sample albedos
Surface: Typical albedo
Fresh asphalt 0.04
Open ocean 0.06
Worn asphalt 0.12
Conifer forest (Summer) 0.08[7] 0.09 to 0.15
Deciduous forest 0.15 to 0.18
Bare soil 0.17
Green grass 0.25
Desert sand 0.40
New concrete 0.55
Ocean ice 0.50 to 0.70
Fresh snow 0.80

Erasmus: . Albedo is highest near the poles and lowest in the subtropics, with a local maximum in the tropics.
Snow albedo is highly variable, ranging from as high as 0.9 for freshly fallen snow, to about 0.4 for melting snow, and as low as 0.2 for dirty snow. Over Antarctica snow albedo averages a little more than 0.8.

Charcoal has an albedo of 0.04 , being one of the one of the darkest substances.

Bitumen roads spanning increasing areas of the planet would have a similarly low albedo.

When seen from a distance, the ocean surface has a low albedo, as do most forests, whereas desert areas have some of the highest albedos among landforms. Most land areas are in an albedo range of 0.1 to 0.4.

For a given area, albedo is determined by more than just the composition of soil, it's impacted by soil moisture, type of vegetation, and levels of urbanization. Different surfaces on the Earth have different albedos and that albedo varies with time.

Changes in albedo occur as the amount of cloud cover changes. Likewise, changes in any surface cover, like snow, ice, and vegetation, shift the albedo.

Earth's average surface temperature due to its albedo and the greenhouse effect is currently about 15 °C (59 °F). If Earth were frozen entirely (and hence be more reflective), the average temperature of the planet would drop below -40 °C (or -40 °F). If only the continental land masses became covered by glaciers, the mean temperature of the planet would drop to about 0 °C (32 °F). In contrast, if the entire Earth was covered by water – a so-called ocean planet – the average temperature on the planet would rise to almost 27 °C (81 °F).

Earths Albedo Diagram Feb 2015
Albedo values for the Earth for February 2015

Erasmus: . Earth’s surface albedo is regularly estimated via Earth observation satellite sensors such as NASA’s MODIS instruments on board the Terra and Aqua satellites, and the CERES instrument on the Suomi NPP and JPSS. As the amount of reflected radiation is only measured for a single direction by satellite, not all directions, a mathematical model is used to translate a sample set of satellite reflectance measurements into estimates of directional-hemispherical reflectance and bi-hemispherical reflectance

Kinkajou:. Let’s look at some of the variables affecting albedo.

Erasmus: .
Trees
Because forests generally have a low albedo, (the majority of the ultraviolet and visible spectrum is absorbed through photosynthesis), some scientists have suggested that greater heat absorption by trees could offset some of the carbon benefits of afforestation (or offset the negative climate impacts of deforestation).

Trees also impact climate in extremely complicated ways through evapotranspiration. The water vapor causes cooling on the land surface, causes heating where it condenses, acts a strong greenhouse gas, and can increase albedo when it condenses into clouds. 

Clouds
Cloud albedo has substantial influence over atmospheric temperatures. Different types of clouds exhibit different reflectivity, theoretically ranging in albedo from a minimum of near 0 to a maximum approaching 0.8. “On any given day, about half of Earth is covered by clouds, which reflect more sunlight than land and water. Clouds keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth.

Albedo and climate in some areas are affected by artificial clouds, such as those created by the contrails of heavy commercial airliner traffic.

A study following the burning of the Kuwaiti oil fields during Iraqi occupation showed that temperatures under the burning oil fires were as much as 10 °C (18 °F) colder than temperatures several miles away under clear skies.

Black carbon
Another albedo-related effect on the climate is from black carbon particles. The size of this effect is difficult to quantify: the Intergovernmental Panel on Climate Change estimates that the global mean radiative forcing for black carbon aerosols from fossil fuels is +0.2 W m?2, with a range +0.1 to +0.4 W m?2.

Black carbon is a bigger cause of the melting of the polar ice cap in the Arctic than carbon dioxide due to its effect on the albedo.

Bitumen and cities are hot and are numerous enough and extensive enough to result in climate changes, something oft forgotten when people start talking about CO2.

Solar Cycle In Climate

Solar Cycle In Climate

Kinkajou:.
In order to predict the climate change, we need to consider the effects of environmental factors on energy retention or energy loss.

1. Clouds cool the Earth by reflecting incoming sunlight. The tiny drops or ice particles in clouds scatter between 20 and 90 percent of the sunlight that strikes them, giving them their bright, white appearance. From space, clouds look bright whereas large bodies of water look dark. A cloud-free Earth would absorb nearly 20 percent more heat from the sun than the present Earth does, creating an Earth warmer by about 12C. Clouds cool the planet by reflecting sunlight back into space, much as they chill a summer's day at the beach.

2. Clouds warm the Earth by absorbing infrared radiation emitted from the surface and reradiating it back down. The process traps heat like a blanket and slows the rate at which the surface can cool. The blanketing effect warms Earth's surface by some 7C.

3. Thus, the net effect of clouds on the climate is to cool the surface by about 5C.

Clouds reflect about 50 W m-2 of solar radiation up into space, and radiate about 30 W m-2 down to the ground, so the net effect is 20 W m-2 cooling on average.

This greatly exceeds the 4 W m-2 warming due to doubling the atmospheric carbon dioxide from 300 to 600 ppm, or the roughly 2 W m-2 cooling caused by aerosols.

Erasmus: . In any event, what matters is only the net effect of clouds. A complicating factor is the altitude of the clouds: high clouds have a net warming effect, because they block little incoming solar radiation but, being so cold, they return little outgoing infrared radiation back to the Earth surface. Low clouds have a net cooling effect, because they have a high albedo, and, being nearly as warm as the surface, they emit nearly as much infrared radiation to space as would the surface under clear skies.

Kinkajou:. There are other factors in climate change which are more important than variables affecting temperature. Ocean chemistry is likely to be very sensitive to the atmospheric carbon dioxide.

Goo: . That’s why I like the term Biosphere Change. The issue is not just about warming. It is really about how human activities are affecting the livability of planet earth – its Biosphere. Warming may be important but ocean acidification from dissolved CO2 is the forgotten issue of climate change/ biosphere change.

Erasmus: . When dissolved in seawater, CO2 creates bicarbonate ions, carbonate ions, carbonic acid (collectively called dissolved inorganic carbon), and hydrogen ions. The oceans are able to absorb large amounts of CO2 from the atmosphere, but it takes 1,000 to 100,000 years for the entire ocean system to become buffered.

The ocean covers approximately 70% of the Earth’s surface, and holds 97% of all water on our planet. There is one connected global ocean, but within it there are 5 recognized oceans: the Arctic, Atlantic, Indian, Pacific, Southern Oceans.

The ocean exchanges these gases with the atmosphere, most important of which is carbon dioxide, so that they remain almost in equilibrium at the ocean surface.

* Rapidly increasing the amount of CO2 dissolved in the surface oceans leads to lower pH of seawater, or increased acidity, which is ocean acidification.
* Ocean acidification is hurting marine life, especially those animals who make calcium carbonate skeletons and shells, as calcium carbonate dissolves in acidic waters.

Goo: . So, you can see that superficial ocean areas like coral reefs are likely to be the most affected by acidification than the open ocean.

the situation gets complex because:

Warmer water temperatures can result in coral bleaching. When water is too warm, corals will expel the algae (zooxanthellae) living in their tissues causing the coral to turn completely white. This is called coral bleaching.
Ocean acidification causes bleaching and productivity loss in coral reef builders. Ocean acidification slows the rate at which coral reefs generate calcium carbonate, thus slowing the growth of coral skeletons. 

Gets complex as you can see.

Erasmus: . Since the Industrial Revolution, the oceans have absorbed approximately 30% of all CO2 released. 

Goo: . What does this do, specifically, to our oceans?
Erasmus: . When carbon dioxide is absorbed by the ocean, it is dissolved into the water. This dissolution of carbon dioxide can lead to the formation of three ‘species of carbon: bicarbonate ions (HCO3–), carbonate ions (CO3 - -), and carbonic acid (H2CO3).

Buffering CO2 by Oceans
> Dissociation of carbon dioxide in seawater.
> > Dissolution of calcite in seawater.

It is important to notice in the above equation that when CO2 and H2O mix, they produce a free hydrogen ion in seawater. This reaction is measured by pH .
The pH scale, which ranges from 0-14, is a scale to measure the amount of hydrogen ion present in an aqueous solution (a solution that contains water), with lower numbers being very acidic, 7 neutral, and higher numbers very basic.

Acids with a very low pH have the ability to burn or dissolve other materials. Thus, acidification is to make a solution become acid or acidic.

The acidity of any substance on the pH scale is measured by the amount of hydrogen ions in the solution, or the hydrogen ion concentration. pH is measured as the negative log of hydrogen ion concentration:

Erasmus: . Ocean Acidification and Buffering
An acid is an ion or molecule that can donate a hydrogen ion (H+). In simpler terms, an acid is a substance that has a sour taste in aqueous solutions, and have a low pH.

The bottom line here is: when there are more hydrogen ions (H+) in a solution, the more acidic it becomes.

Buffering by Carbonate Dissolution.
The bottom of the ocean contains carbonate shells of organisms, most of which come from planktic foraminifera. These are single-celled marine plankton, living in the open ocean and secreting a calcite shell (or test). These are generally about the size of a small grain of sand, can have spines or holes of many different shapes and sizes. The planktic forams, those that live in the upper water column, and benthic forams, those that live on the seafloor or within ocean sediments.

 In the presence of acidic solutions, these calcite sediments, the carbonate shells, will dissolve. But remember, it takes a very long time for the surface ocean and deep ocean to mix (~1,000 years), so buffering by fossils on the seafloor is not instantaneous.

By the below equation, calcite dissolves to produce a calcium ion and two bicarbonate ions:

As calcite sediments on the seafloor dissolve with the addition of carbon dioxide, these produce more bicarbonate ions. The addition of bicarbonate ions will lead to buffering by moving to the left and producing more carbonic acid in seawater.

Thus, the buffering capacity of the ocean, or its ability to resist a change in pH, is actually quite large. In general, the ocean contains around 38,000 gigatons (or 38 billion tons) of bicarbonate, carbonate, and carbonic acid. So, the world oceans can absorb a lot of CO2 without increasing their acidity.(This is called buffering).

Goo: . I have been told that this process takes a lot of time.

Erasmus: . The atmosphere and the surface ocean exchange gases on a rate of 10-100 years, the surface ocean and deep ocean mix on a scale of about 1,000 years. The calcite sediments on the ocean floor are only important as buffers after the surface and deep ocean layers have mixed. Therefore, the timescale on which the bottom sediments can buffer the oceans is on a timescale between 1,000-100,000 years 

Thus, once anthropogenic carbon emissions cease, the entire ocean will eventually absorb the excess carbon dioxide, which will be neutralized. But, this will take at least 1,000 years. Therefore, the amount of carbon dioxide being released by humans today is in part a massive problem because the rate at which it is being released. Our oceans simply can’t keep up.

Chart showing increasing atmospheric carbon dioxide concentrations and falling pH in the surface ocean.

The red Line is the amount of CO2 in the atmosphere;
the green data points are the partial pressure of CO2 in seawater;
the blue data points are surface ocean pH measurements.
The black lines in each data series represent the average trends through time.

Notice that as atmospheric CO2 increases, pH in the surface oceans is rapidly declining (becoming more acidic).

Scientists state that the oceans have absorbed about 30% of all CO2 that has been put into the atmosphere by humans since the Industrial Revolution. Scientists have concluded that this has led to a 26% increase in the acidity of our oceans. The rate at which the oceans are becoming more acidic is totally unprecedented, and research indicates that ocean acidification is happening faster today than at any time in the last 300 million years.

Thus, as our oceans become more acidic, animals that build their skeletons and shells from calcite are becoming more stressed. It is becoming increasingly harder for these animals to build their skeletons and shells.

Goo: . So, we have yet to see the impact of oceanic acidification on the Earth’s biosphere. Whether acidification is a factor in coral effects or if simply temperature is the main variable affecting coral growth would be interesting to consider.

There is another factor as well. CO2 is actually essential for life and especially for photosynthesis. So, a lot of the carbon dioxide will be absorbed into plant materials (phytoplankton) which then deposit in the final analysis on the ocean floor.
Fossil fuels are mostly created by the anaerobic decomposition of buried plant matter, usually over the course of millions of years.

Erasmus: . Well Done Goo.

The other obvious issue is that oceanic plant life turns the CO2 into organic matter which then falls to the ocean bottoms.

You have discovered the oceanic coals of earth a billion years in the future. When humanity is extinct, the new masters of earth in a Billion years will marvel at the copious depth of phytoplankton blanketing the bottoms of many of the world’s oceans which has compressed into coal over the billion years- fuel for another industrial revolution for the new inheritors of Earth after humanity has become extinct or moved on.

Kinkajou:. Let’s move on. How do greenhouse gases trap heat in the atmosphere?

Erasmus: . . Greenhouse gas molecules in the atmosphere absorb light, preventing some of it from escaping the Earth. This heats up the atmosphere and raises the planet’s average temperature. The frequency / energy of the radiation is just at the right energy level to be absorbed by chemical bonds in the molecules of the atmosphere. Once absorbed , they will be released generally as lower frequency radiation: especially heat or infrared.

Greenhouse gas molecules will absorb that light, causing the bonds between atoms to vibrate. This traps the energy, which would otherwise go back into space, and so has the effect of heating up the atmosphere.” Basically, the bonds between the carbon and oxygen atoms in our CO2 molecule bend and stretch to absorb photons. (With other greenhouse gases, the molecular bonds are different, but in all cases, they absorb photons, stopping them from leaving the atmosphere.)

Eventually, our CO2 molecule will release these photons. Sometimes, the photons continue out into space. But other times, they rebound back into the Earth’s atmosphere, where their heat remains trapped.

Kinkajou:. What do CO2, methane, and water vapor have in common?

Erasmus: . They are all greenhouse gases.  These Greenhouse gases trap heat in the atmosphere, in a process called the “greenhouse effect.”1 

And importantly, greenhouse gases don’t absorb all photons that cross their paths. Instead, they mostly take in photons leaving the Earth for space. “CO2 molecules absorb infrared light at a few wavelengths, but the most important absorption is light of about 15 microns,” Incoming light from the sun tends to have much shorter wavelengths than this, so CO2 doesn’t stop this sunlight from warming the Earth in the first place. But when the Earth re-emits this light, it has a longer wavelength, in the infrared spectrum.

And the range of wavelengths around 15 microns is a particularly crucial window. The most common greenhouse gas, water vapor, doesn’t efficiently absorb photons in this range. So, when CO2 grabs photons with wavelengths around 15 microns, it’s selecting for the same light that normally has the easiest time escaping Earth’s atmosphere.

There’s another reason why CO2 is such an important greenhouse gas: it has a long atmospheric lifetime..
Methane, another greenhouse gas, reacts easily with oxygen, which removes it from the atmosphere within around 12 years. That’s long enough to affect the climate, but nowhere near the lifetime of CO2, which does not react with oxygen and can last over a century.

CO2’s long lifespan is the key reason that human activities are leading to climate change. As we keep taking carbon-based compounds like coal and oil out of the ground, and put that carbon in the atmosphere in the form of CO2, the added CO2 piles up much faster than it can be naturally removed.

The annual amount of CO2 we emit from using carbon that was in relatively long-term sequestration (coal, natural gas, petroleum) is on the order of 40 GT. To put this in perspective: the amount of food humans consume over the same period of time is on the order of 4 GT. Our CO2 production is an order of magnitude larger than worldwide food consumption. And the problem with it is that it takes weathering to remove it from the atmosphere - meaning it can stay around for millennia, and we're very definitely the ones extracting it from the ground.

H2O only stays in the atmosphere as long as the temperature allows. This means that it won't be the driving factor. There is slight positive feedback with more H2O leading to a warming so it can hold more H2O, but there's also negative feedback of about the same size with cloud formation reflecting the sunlight back to space.

Erasmus: . Water vapor is the most common greenhouse gas, and the one with the greatest overall effect on atmospheric heat retention. Due to the enhanced greenhouse effect, levels of water vapor in the atmosphere increase due to a positive feedback loop. Warmer conditions cause increased evaporation of water, with the warmer atmosphere able to hold larger amounts of water vapor. Therefore, when human greenhouse emissions cause warming, increased water vapor levels are a secondary effect. The higher water vapor levels then trap yet more heat, creating the feedback loop.

Ozone in the upper atmosphere is responsible for the warming at the Stratopause. It's the reason why we have our atmosphere divided into layers with the Troposphere getting cooler with height, the Stratosphere getting warmer with increased height, and the Mesosphere getting cooler again with height

CH4 stays in the atmosphere on the order of a decade before chemically reacting with oxygen molecules to become CO2 and H2O - but while it's present, the effect is about two orders of magnitude greater than that of CO2. But since the methane hydrates have been stable in their levels in the atmosphere, they're not culpable in the warming.

Although there are large quantities in tundra and ocean shelves, there's little point in making it the talking factor for anything except scare tactics.

This CH4 is currently less than 2 ppmv and CO2 is over 400 ppmv, making CO2 easily the biggest factor in our warming.

Some scientists believe that the warming from CO2 is what's causing the tundra to melt and the East Siberian Arctic Shelf (the largest on the planet) to warm and release its methane.
This is why we concentrate on CO2 (it being the largest factor and also the only one we seem to have much control over).

Kinkajou:. . Let’s consider Greenhouse Gases and Their Sources

Erasmus: . . Some greenhouse gases are emitted exclusively from human activities (e.g., synthetic halocarbons).

Others occur naturally but are found at elevated levels due to human inputs (e.g., carbon dioxide).

Anthropogenic sources result from energy-related activities (e.g., combustion of fossil fuels in the electric utility and transportation sectors), agriculture, land-use change, waste management and treatment activities, and various industrial processes.

Major greenhouse gases include carbon dioxide, methane, nitrous oxide, and various synthetic chemicals.

* Water Vapour is the most important greenhouse gas in terms of quantity and effect on climate.
* Low clouds reflect more heat and radiate more heat than high clouds

Carbon dioxide 
* Approximately two-thirds of human-caused carbon dioxide comes from burning fossil fuels, with an additional third resulting from deforestation. Carbon is stored in plant matter, such as trees and plants, within forests.

When fossil fuels are burned, and forests destroyed, the stored carbon is released into the atmosphere as carbon dioxide. As of 2011, atmospheric carbon dioxide levels were approximately 35 percent above normal, and rising.

* Methane comes from many sources, including human activities such as coal mining, natural gas production and distribution, waste decomposition in landfills, and digestive processes in livestock and agriculture. Natural sources of methane include wetlands and termite mounds.

While carbon dioxide is typically painted as the bad boy of greenhouse gases, Methane, the main component of natural gas, is a potent greenhouse gas that traps about 20 times as much heat as carbon dioxide. Atmospheric methane emissions occur during natural gas drilling, coal mining and other industrial processes. The digestive systems of livestock produce approximately 35 percent of human-caused methane emissions. Some scientists predict that warming trends will melt arctic permafrost, resulting in large releases of methane, and a positive feedback loop that will accelerate global warming.

* New research in the journal Nature indicates that for each degree that  Earth's temperature rises, the amount of methane entering the atmosphere from microorganisms dwelling in lake sediment and freshwater wetlands -- the primary sources of the gas -- will increase several times.

* As temperatures rise, the relative increase of methane emissions will outpace that of carbon dioxide from these sources, the researchers report.

* In freshwater systems, methane is produced as microorganisms digest organic matter, a process known as "methanogenesis." This process hinges on a slew of temperature, chemical, physical and ecological factors that can bedevil scientists working to model how Earth's systems will contribute, and respond, to a hotter future.

* The researchers' findings suggest that methane emissions from freshwater systems will likely rise with the global temperature. But to not know the extent of methane contribution from such a widely dispersed ecosystem that includes lakes, swamps, marshes and rice paddies leaves a glaring hole in climate projections.

* The researchers found that a common effect emerged from those studies: freshwater methane generation very much thrives on high temperatures. Methane emissions at 0 degrees Celsius would rise 57 times higher when the temperature reached 30 degrees Celsius,

* Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels.

Nitrous oxide exists in much smaller concentrations in the atmosphere, but is a very efficient greenhouse gas, trapping approximately 300 times as much heat as carbon dioxide. Human nitrous oxide emissions are produced mainly by the agricultural sector. When nitrogen-rich fertilizers make their way into underground aquifers and rivers, they breakdown to produce atmospheric nitrogen, with nitrous oxide as a by-product. Human-caused nitrous oxide emissions account for between 6 and 10 percent of the enhanced greenhouse effect.

It is the opinion of many climate scientists that Multiple lines of evidence suggest that human activities are the primary cause of the global warming of the past 50 years. 
Natural factors, such as variations in the sun's output, volcanic activity, the Earth's orbit, the carbon cycle, and others, also affect Earth's radiative balance. These are often discounted and some factors such as meteor related solar fluorescence in the UV region is something very few scientists have ever even considered as a climate variable.

However, beginning in the late 1700s, the net global effect of human activities has been a continual increase in greenhouse gas concentrations.

* Various synthetic chemicals, such as hydrofluorocarbons, perfluorocarbons, sulphur hexafluoride, and other synthetic gases, are released as a result of commercial, industrial, or household uses.

Kinkajou:. Are there any other radiatively important substances: 
Erasmus: . Certain substances are technically not greenhouse gases due to their physical state, but they nonetheless affect the Earth's energy balance. Some of them, such as sulphate aerosols, have negative radiative forcings that can lead to cooling effects. Others, such as black carbon or soot, contribute to warming.

it would take thousands of molecules of carbon dioxide to equal the warming effect of a single molecule of sulphur hexafluoride—the most potent greenhouse gas
Intergovernmental Panel on Climate Change (IPCC)

 To facilitate comparisons between gases that have substantially different properties, the IPCC has developed a set of metrics called “global warming potentials.”

Atmospheric Layers

Goo: . Let’s Talk about the Impacts of Biosphere Change.

Erasmus: . The changing climate affects society and ecosystems in a variety of ways

The ROE presents six indicators showing trends in greenhouse gas emissions and their associated environmental impacts: Greenhouse Gas Emissions, Greenhouse Gas Concentrations, Energy Use, Temperature and Precipitation, Sea Level, and Sea Surface Temperature.
A warmer climate is expected to both increase the risk of heat-related illnesses and deaths and increase certain types of air pollution.

* More severe heat waves, floods, and droughts are expected in a warmer climate. These may reduce crop yields.

* Sea level rise could erode and inundate coastal ecosystems and eliminate wetlands.

* Climate change can alter where species live and how they interact, which could fundamentally transform current ecosystems.

* Emissions. For several greenhouse gases, the nation's estimated combined emissions that are directly attributable to human activity have increased 7 percent between 1990 and 2014. Fossil fuel combustion is the country's major source of anthropogenic greenhouse gas emissions.

* Concentrations. Data on atmospheric concentrations of greenhouse gases have exceptionally long historical records, with data for some gases spanning several hundred thousand years. For carbon dioxide, methane, and nitrous oxide, the historical context provided by ice cores shows that present atmospheric concentrations are unprecedented over the last 800,000 years, and demonstrate that the recently increasing levels reflect the influence of human activity.

* Impacts.  Average temperatures across the contiguous 48 states have increased since 1901, with an increased rate of warming since the late 1970s.

Total annual precipitation has increased in the United States and over land areas worldwide. Since 1901, total precipitation in the contiguous 48 states has increased at an average rate of 0.17 inches per decade.

Ocean surface temperatures increased around the world during the 20th century and the average surface temperatures during the past three decades have been higher than at any other time since widespread measurement began in the late 1800s.

Finally, when averaged over all the world's oceans, sea level rise is debated. Some projections say change has occurred within limits of current system variability. Others asset that world sea level has increased at a rate of roughly six-tenths of an inch (13-17mm) per decade since 1880, and the rate of increase has accelerated in recent years to more than an inch per decade.

Glacier

Kinkajou:. There was an Australian politician who was roasted by the media for his opinion on climate change and sea level rise. His issue. He had been a surf life saver for over 40 years and had seen no noticeable effects on the sea level in his beachside surf side in that tide.

Goo: . It demonstrates the clash between politics and science That man said that it has not happened by his own observations over 40 years.

Erasmus: . Context and real-life experience do matter.
Just because you can calculate that rises are occurring using one dataset, does not mean that others can debunk your claims using other data sets.

Goo: . What matters is what do you see as “really “happening.

Erasmus: . * There are a few limitations associated with the ROE greenhouse gas indicators.

* Emissions. The emissions trends are based largely on estimates, which have uncertainties inherent in the underlying engineering calculations and estimation methodologies.
One gap in the emissions indicator is that EPA's greenhouse gas inventory does not track every greenhouse gas or every emissions source.

The most notable sources not tracked in the inventory are natural sources, such as methane from wetlands, carbon dioxide and methane from thawing permafrost, and multiple emissions from volcanoes.

* Concentrations. While the concentration data thoroughly characterize trends for carbon dioxide (the most important anthropogenic greenhouse gas) and other extensively studied gases, comprehensive global data are not available for other radiatively important substances, such as soot and aerosols.

Though these substances technically are not greenhouse gases, tracking trends in these substances' concentrations is important due to their ability to alter the Earth's energy balance.

* Impacts. The changing climate can affect society and ecosystems in many ways. For example, climate change can alter the likelihood of extreme weather events, influence agricultural crop yields, affect human health, cause changes to forests and other ecosystems, and even impact energy supplies. ROE indicators were developed for a few climate measures that are most directly linked to greenhouse gas emissions and concentrations and that have particularly long and abundant records.

Kinkajou:. So What do you see as the main issues, Goo?

Goo: . I think we should be talking about Biosphere change not global warming or climate change. The key issue is how human activities working along with or against natural process are changing the liveability of our planet.

The next issue is what changes can we make to improve the liveability of our planet for humanity and for all the other plants and animals on the planet for which we are the custodians.

The increase in earth temperatures is perhaps the result of increased solar affects gradually changing Earth’s albedo as the ice melts. However, we need to be aware of UV changes in solar irradiation as a mechanism for biosphere changes unfavourable to the earth’s biosphere. And this change may not be a natural event.

Oceanic acidification is a critical issue. Whether we can afforest the oceans and increase carbon sequestration in the depths of the ocean is certainly a new frontier for humanity.

Human activities affect all the plants and animals on the planet. We need to be aware of our responsibility for acting as a buffer to life threatening processes that affect our planet.

Erasmus: . One Sci-Fi author; Charles Stross in the book Saturn’s Children makes the point we need to be careful not to have a runaway greenhouse effect boiling all life on the planet – in effect making the earth like the planet Venus. If we are careless, it could be our constructs – robots- who end up inheriting our Earth.

Dr Axxxx: . But never forget, we are not alone in the Universe. The Fermi effect is real. Where are all the alien species/ It looks likely that while we act to improve our situation on planet Earth, it is in the interests of others with greater knowledge and science, to act in an opposing fashion.

Report: When Rains Turn to Dust : ICRC

International Committee of the Red Cross